49. London Planetree

(London Planetree)

Platanaceae

Platanus x hybrida

Specimen Size: 63.2ft tall, 20.75in in diameter.

Historical Background: More than 100 hybrid Planetrees, or Sycamores, placidly overhang Memorial Way. The original 57 were planted in 1920 as memorials for UW faculty and students killed in the first World War. These trees are appropriate for the role, being monumentally large and long lived. The eastern United States sycamore (Platanus occidentalis) crossed with its Old World counterpart (P. orientalis) resulted in this vigorous offspring that have been planted since the late 1600s.

Non-native

Native Range: Believed to be hybrid between native sycamore and non-native Asian planetree.

Identifying Features: This tree is a hybrid between Platanus occidentalis and Platanus orientalis, producing a hybridization between the features of the two distinct Sycamore species. The London Plane is a different type of cross between the P. occidentalis and P. acerfolia. The London Plane hybrid grows taller with paler bark and droopier branches than these specimens. The leaves are maple-like, light green in color, but have rather short stalks. Round seed heads dangle on stout string-like stalks. The fall foliage color is drab yellow-brown, but the exfoliating patchy bark mottles the trunks handsomely, especially in severe winter cold.

Identifying Features In Depth:

Form: Large tall trees breaking into multiple stems and ascending branches which create a large bulbous or rounded crown of thick foliage above the open graceful branches in the center. It can reach a height of 165’ (50m).
Leaves: Leaves are palmate in venation, and exhibit 5-7 shallow lobes, appearing broadly ovate with the teeth appearing at the tip of each significant vein. They are glabrous except along veins, with cordate (heart shaped) bases on new growth. Veins are prominent and generally a lighter green than the rest of the leaf.
Bark: Bark is very distinctive, smooth at first and almost white, but exfoliating with age to reveal puzzle piece shaped or square patches of yellow, white, and green underbark.
Reproductive Bodies: Flowers appear with new leaves, males and females appear on separate heads on the tree, and are small rounded greenish balls on a long petiole. The Fruit is likewise a rounded ball, 1 ½ ” (4cm) in diameter and rough, a light brown. It is tipped with small brown hairs.

Planetrees or Sycamores?

The London Plantree is a hybrid species, a cross between the American Sycamore (Platanus occidentalis) and the Oriental Planetree (Platanus occidentalis). These two parent species have been separated by the Atlantic Ocean for millions of years, but were obviously still closely enough related to produce offspring together. So why the difference in names between "Planetree" and "Sycamore"? This quirk of naming is a frequent occurrence with what we call "common names", or the names used in day to day life to describe plants and animals. Since species often cover broad ranges, and human languages vary widely and often include regional dialects, it is not uncommon for species to end up with multiple ways of describing them, and for closely related species to have wildly different names (like in the case with our Planetrees and Sycamores). The video to the right shares a bit about another member of this Genus, the California Sycamore, which lives on the west coast of North America.

Below is the description found for this species on the original Brockman Memorial Tree Tour:

Historic Tree Tour Information: More than 100 hybrid Planetrees, or Sycamores, placidly overhang Memorial Way. The original 57 were planted in 1920 as memorials for UW faculty and students killed in the first World War. These trees are appropriate for the role, being monumentally large and long lived. The eastern United States sycamore (Platanus occidentalis) crossed with its Old World counterpart (P. orientalis) resulted in this vigorous offspring that have been planted since the late 1600s. The leaves are maple-like, but have rather short stalks. Round seed heads dangle on stout string-like stalks. The fall foliage color is drab yellow-brown, but the exfoliating patchy bark mottles the trunks handsomely, especially in severe winter cold. The most famous of these hybrid clones is the one called London Plane, which grows taller with paler bark and droopier branches than our campus trees.

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